Bump structure, wiring substrate, semiconductor apparatus and bump structure manufacturing method

ABSTRACT

A bump structure provided on an electrode pad includes a solder member, and a metal layer having a cylindrical portion covering a side surface of the solder member, the metal layer being made of a metal which is higher in melting point than the solder member. An upper part of the cylindrical portion of the metal layer is opened wide.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of priority of JapanesePatent Application No. 2013-155615 filed on Jul. 26, 2013. Thedisclosures of the application are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a bump structure, a wiring substrate, asemiconductor apparatus, and a bump structure manufacturing method.

2. Related Art

Recently, the advancement and the complication of electronic productshave reduced the pitches of bumps of electronic elements. As a method offorming narrow pitch bumps of a semiconductor chip, whose bump pitch issmall, a technique is known in which a copper post is formed on eachelectrode pad on a semiconductor chip and in which an opening on eachcopper post is filled with solder (see JP-A-2009-177118).

However, in a related-art bump structure, when a semiconductor chip ismounted on a wiring substrate, sometimes, solder is crushed, and abridge occurs between adjacent bumps.

SUMMARY

Exemplary embodiments of the invention provides a bump structure, awiring substrate, a semiconductor apparatus, and a method ofmanufacturing a bump structure, each of which can prevent occurrence ofa bridge between bumps.

A bump structure provided on an electrode pad according to an exemplaryembodiment of the invention, comprises:

a solder member; and

a metal layer having a cylindrical portion covering a side surface ofthe solder member, the metal layer being made of a metal which is higherin melting point than the solder member, wherein

an upper part of the cylindrical portion of the metal layer is openedwide.

A method of manufacturing a bump structure provided on an electrode pad,according to an exemplary embodiment, comprises:

forming a first resin layer on the electrode pad; forming, on the firstresin layer, a second resin layer differing in peeling-property from thefirst resin layer;

forming, in each of the first resin layer and the second resin layer, afirst opening whose upper part is opened wide;

forming, on an inner wall of the first opening, a metal layer made of ametal which is higher in melting-point than a solder member;

filling the solder member in the metal layer; and

removing the second resin layer.

According to a bump structure, a wiring substrate, a semiconductorapparatus, and a method of manufacturing a bump structure of theexemplary embodiments, it is possible to prevent occurrence of defectssuch as a bridge between the adjacent bumps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram illustrating a wiring substratehaving a bump structure according to a first embodiment.

FIG. 2 is a cross-sectional diagram illustrating a semiconductorapparatus configured such that a semiconductor chip is mounted on thewiring substrate having the bump structure according to the firstembodiment.

FIG. 3 is a cross-sectional diagram illustrating the semiconductorapparatus according to the first embodiment when a manufacturing erroroccurs.

FIGS. 4A to 7C are process cross-sectional diagrams illustrating amethod of manufacturing the bump structure according to the firstembodiment.

FIG. 8 is a cross-sectional diagram illustrating a wiring substratehaving a bump structure according to a second embodiment.

FIG. 9 is a cross-sectional diagram illustrating a semiconductorapparatus configured such that a semiconductor chip is mounted on thewiring substrate having the bump structure according to the secondembodiment.

FIGS. 10A to 13C are process cross-sectional diagrams illustrating amethod of manufacturing the bump structure according to the secondembodiment.

FIG. 14 is a cross-sectional diagram illustrating a wiring substratehaving a bump structure according to a third embodiment.

FIGS. 15A to 15C are process cross-sectional diagrams illustrating amethod of manufacturing the bump structure according to the thirdembodiment.

DETAILED DESCRIPTION First Embodiment

A bump structure according to a first embodiment is described withreference to FIGS. l to 7C.

Wiring Substrate

A wiring substrate having a bump structure according to the firstembodiment is described with reference to FIG. 1. FIG. 1 is across-sectional diagram illustrating a wiring substrate having a bumpstructure according to the present embodiment.

A wiring substrate 10 is a buildup substrate using, e.g., an insulatinglayer made of resin, and a core substrate. Electrode pads 12 and 30 areprovided on an insulating layer. An internal structure of the wiringsubstrate 10 is indicated with dashed lines in FIG. 1. Thus, thedetailed description of the internal structure is omitted.

Incidentally, the internal structure of the wiring substrate 10 is notlimited to that illustrated in FIG. 1. Any structure may be used as theinternal structure of the wiring substrate 10. For example, variouswiring substrates such as a coreless substrate may be used as the wiringsubstrate 10.

In FIG. 1, the top surface of the wiring substrate 10 is achip-mounting-surface on which a semiconductor chip (not shown) ismounted. The bottom surface of the wiring substrate 10 is amotherboard-connection-surface connected to a motherboard (not shown).

Plural electrode pads 12 are formed on a chip-mounting-surface of thewiring substrate 10 at a small pitch compatible with the pitch of pluralelectrode posts (not shown) of a semiconductor chip (not shown) to bemounted.

The electrode pads 12 are formed, e.g., circularly. The electrode pads12 are, e.g., 50 micrometers (μm) in diameter. The diameter of theelectrode pads 12 may be within a range of 30 μm to 100 μm. Theelectrode pads 12 are 15 μm in thickness. The thickness of the electrodepads 12 may be within a range of 5 μm to 20 μm.

The pitch of the plural electrode pads 12 is, e.g., 75 μm and may bewithin a range of 60 μm to 120 μm.

The electrode pads 12 are made of copper, copper alloy or the like.

On the chip-mounting-surface of the wiring substrate 10, an insulatingresin layer 14 is formed so as to cover the entire electrode pads 12.The thickness of the insulating layer 14 on the surface of eachelectrode pad 12 is 15 μm. The insulating layers 14 are formed of apermanent resist made of an epoxy-based resin or acryl-based resin suchas a solder resist.

An opening 15 tapered to be opened wide at an upper part is formed oneach electrode pad 12 in the insulating resin layer 14.

In the tapered-shape opening 15 in the insulating resin layer 14,electrically conductive layers 16 are formed on the electrode pads 12,respectively. The electrically-conductive layer 16 is a Ni/Pd/Au platinglayer which Ni-layer, Pd-layer, and Au-layer are sequentially stacked bythe electroless plating from the bottom side as viewed in FIG. 1. Thethickness of Ni-layer is, e.g., 5 μm and may be within a range of 0.05μm to 10 μm. The thickness of Pd-layer is, e.g., 0.1 μm and may bewithin a range of 0.02 μm to 0.2 μm. The thickness of Au-layer is, e.g.,0.1 μm and may be within a range of 0.01 μm to 0.5 μm.

Each metal layer 20 is formed via a seed layer 18 on anelectrically-conductive layer 16 in the tapered-shape opening 15 in theinsulating resin layer 14 and on the side wall of the opening 15. Eachof the seed layer 18 and the metal layer 20 is such that the bottom sidethereof is embedded in the insulating resin layer 14 and that the topside thereof is protruded upwardly from the insulating resin layer 14.

The metal layer 20 includes a bottom portion 20 a and a cylindricalportion 20 b that is formed integrally with the bottom portion 20 a andopened wide at an upper part. A solder member (solder bump) 22 is formedby filling the inside of the cylindrical portion 20 b of the metal layer20 with solder.

The solder member 22 is shaped like an inverted truncated-cone inconformity with the shape of the cylindrical portion 20 b whose upperpart is opened wide.

The metal layer 20 is, e.g., 2 μm in thickness and may be within a rangeof 0.5 μm to 5 μm in thickness.

The seed layer 18 is, e.g., 0.5 μm in thickness and may be within arange of 0.2 μm to 2 μm in thickness.

The shape of the cylindrical portion 20 b of the metal layer 20, whichis widened upward, is a tapered-shape configured such that, e.g., thediameter of a bottom outer-circumference is 40 μm, the diameter of a topouter-circumference is 55 μm, a height is 40 μm, and a spread-angle is10 degrees.

The shape of the cylindrical portion 20 b of the metal layer 20, whichis widened upward, may be a tapered-shape configured such that thediameter of a bottom outer-circumference is within a range of 30 μm to60 μm, the diameter of a top outer-circumference is within a range of 40μm to 100 μm, a height is within a range of 25 μm to 60 μm, and aspread-angle is within a range of 5 degrees to 30 degrees.

The solder of the solder member 22 is, e.g., Sn, Sn—Zn alloy, Sn—Cualloy, Sn—In alloy, Sn—Ag alloy, or the like.

The metal layer 20 is formed using a metal whose melting point is higherthan the eutectic point (melting point) of the solder member 22. Themetal layer 20 is made of metal, e.g., Ni, Co, or the like.

For example, if the solder member 22 is Sn, the metal layer 20 is madeof metal, e.g., Ni, whose melting point is higher than 232 degreescentigrade (° C.) which is the melting point of Sn. The seed layer 18 ismade of Cu.

Thus, on a surface of the wiring substrate 10, on which a semiconductorchip is mounted, plural bump structures 24 each including the metallayer 20 and the solder member 22, with which the inside of the metallayer 20 is filled, are formed.

On the motherboard-connection-surface of the wiring substrate 10, whichis connected to the motherboard, plural electrode pads 30 are formed ata pitch compatible with the pitch of plural electrodes (not shown) ofthe motherboard (not shown) on which the wiring substrate 10 is mounted.

The electrode pads 30 are made of, e.g. copper, copper alloys, or thelike. The electrode pads 30 are 15 μm in thickness. The thickness of theelectrode pads 30 may be within a range of 5 μm to 20 μm. Each electrodepad 30 is, e.g., 200 μm in diameter. The diameter of each electrode pad30 may be within a range of 50 μm to 1000 μm.

The pitch of the plural electrode pads 30 is compatible with the pitchof plural electrodes (not shown) of the motherboard (not shown) andwithin in a range of, e.g., 300 μm to 1500 μm.

An insulating layer 32 is formed on the surface of the wiring substrate10, which is connected to the motherboard to cover the electrode pads30. The thickness of the insulating layer 32 from the surface of eachelectrode pad 30 is 15 μm. The insulating layer 32 is formed of apermanent resist made of an epoxy-based resin or acryl-based resin suchas a solder resist.

An opening 33 is formed on each electrode pad 30 in the insulating layer32. An electrically-conductive layer 34 is formed on each electrode pad30.

The electrically-conductive layer 34 is configured similarly to theelectrically-conductive layer 16 on the surface of the wiring substrate10, on which the chip is mounted. For example, in FIG. 1, theelectrically-conductive layer 34 is a Ni/Pd/Au plating layer in whichNi-layer, Pd-layer, and Au-layer are stacked sequentially from the topside. The thickness of Ni-layer is, e.g., 5 μm and may be within a rangeof 0.05 μm to 10 μm. The thickness of Pd-layer is, e.g., 0.1 μm and maybe within a range of 0.02 μm to 0.2 μm. The thickness of Au-layer is,e.g., 0.1 μm and may be within a range of 0.01 μm to 0.5 μm.

A solder member (solder bump) 36 is formed on eachelectrically-conductive layer 34. The solder of the solder member 36 is,e.g., Sn, Sn—Zn alloy, Sn—Cu alloy, Sn—In alloy, Sn—Ag alloy, or thelike.

Incidentally, the electrically-conductive layers 16 and 34 are notlimited to the above Ni/Pd/Au plating layers.

For example, the electrically-conductive layers 16 and 34 may be Ni/Auplating layers in each of which Ni-layer and Au-layer are stacked. Thethickness of Ni-layer is, e.g., 5 μm and may be within a range of 0.05μm to 10 μm. The thickness of Au-layer is, e.g., 0.05 μm and may bewithin a range of 0.01 μm to 0.5 μm.

Alternatively, the electrically-conductive layers 16 and 34 may beAu-plating-layers. The thickness of Au-plating-layer is, e.g., 0.05 μmand may be within a range of 0.01 μm to 0.5 μm.

Alternatively, the electrically-conductive layers 16 and 34 may be Pd/Auplating layers in each of which Pd-layer and Au-layer are stacked. Thethickness of Pd-layer is, e.g., 0.1 μm and may be within a range of 0.02μm to 0.2 μm. The thickness of Au-layer is, e.g., 0.05 μm and may bewithin a range of 0.01 μm to 0.5 μm.

Alternatively, the electrically-conductive layers 16 and 34 may be Agplating layers. The thickness of Ag-layer is, e.g., 0.1 μm and may bewithin a range of 0.02 μm to 0.5 μm.

Semiconductor Apparatus

A semiconductor apparatus configured by mounting a semiconductor chip ona wiring substrate having a bump structure according to the presentembodiment is described below with reference to FIG. 2. FIG. 2 is across-sectional diagram illustrating a semiconductor apparatusconfigured such that a semiconductor chip is mounted on a wiringsubstrate having a bump structure according to the present embodiment.

As illustrated in FIG. 2, plural electrode posts 42 are formed at asmall pitch on a semiconductor chip 40 to be mounted. The electrode post42 is, e.g., a columnar electrode post formed by copper-plating or thelike.

The plural electrode pads 12 on the chip-mounting-surface of the wiringsubstrate 10 are formed at a pitch such that this pitch is compatiblewith the pitch of the plural electrode posts 42 of the semiconductorchip 40. The plural bump structures 24 each including the metal layer 20and the solder member 22 are respectively formed on the plural electrodepads 12 so that the pitch of the plural bump structures 24 is compatiblewith the pitch of the plural electrode posts 42 on the semiconductorchip 40.

The plural electrode posts 42 on the semiconductor chip 40 arerespectively joined to the plural bump structures 24 on the wiringsubstrate 10.

Thus, a semiconductor apparatus is formed by mounting the semiconductorchip 40 on the wiring substrate 10.

As described above, according to the present embodiment, each soldermember 22 is covered around with the metal layer 20 whose melting pointis higher than the melting point of solder. Thus, when the electrodeposts 42 on the semiconductor chip 40 are respectively connected to thesolder members 22, the molten solder member 22 can be prevented frombeing crushed and being laterally spread. In addition, because thesolder member 22 is covered around with the metal layer 20, the growthof whisker due to the recrystallization of solder can be suppressed.Accordingly, the adjacent solder members 22 can be preventedelectrically connected and short-circuited by the crushed solder member22 or the whisker growing from the solder member 22.

It is desirable that the plural electrode pads 12 on thechip-mounting-surface of the wiring substrate 10, and the solder members22 are formed at a small pitch with good accuracy so as to be compatiblewith the pitch of the electrode posts 42 on the semiconductor chip 40 tobe mounted. However, a manufacturing error may occur. According to thepresent embodiment, each solder member 22 is tapered to be widenedupward. Thus, a substantial joint part is large. Accordingly, even if adeviation of a formation-position, at which each bump structure 24 isformed, from the corresponding electrode post 42 on the semiconductorchip 40 occurs, each bump structure 24 can favorably be connected to thecorresponding electrode 42.

For example, even if the formation-positions, at which three soldermembers 22 on a left-side part of the wiring substrate 10 arerespectively formed, are deviated rightward from the properformation-positions, as viewed in FIG. 3, the solder members 22 can berespectively connected to the electrode posts 42 on the semiconductorchip 40, as long as the deviation of each formation-position is within arange of the widened upper part of each of the solder members 22.

According to the present embodiment, each solder member 22 is tapered tobe widened upward. Thus, the substantial joint part of each soldermember 22 is large. Consequently, the accuracy of the positionadjustment of the wiring substrate 10 and the semiconductor chip 40 canbe alleviated.

In recent years, with reduction in thickness of the wiring substrate 10,the warpage of the wiring substrate 10 has become more likely to occur.When the wiring substrate 10 is warped, the plural solder members 22 onthe wiring substrate 10 become uneven in height. Thus, the semiconductorchip 40 is moved closer to the wiring substrate 10 so that all theelectrode posts 42 are connected to the solder members 22. According tothe present embodiment, even if the semiconductor chip 40 is put closerto the wiring substrate 10, the solder members 22 can be prevented bythe cylindrical portion 22 b of the metal layer 20 from being crushedand spread laterally. Consequently, the adjacent solder members 22 canbe prevented from being electrically connected and short-circuited.

In addition, even when the wiring substrate 10 is warped, the topsurfaces of the plural solder members 22 formed on the wiring substrate10 can be made flush with one another if the bump structures aremanufactured by a manufacturing method to be described below.Accordingly, the semiconductor chip 40 can favorably be connected to thewiring substrate 10.

Bump Structure Manufacturing Method

A manufacturing method for a bump structure according to the presentembodiment is described below with reference to FIGS. 4A to 7C. FIGS. 4Ato 7C are process cross-sectional diagrams illustrating a method ofmanufacturing a bump structure according to the present embodiment.

First, an insulating resin layer 14 is formed to cover the entireelectrode pads 12 serving as an outermost layer of the wiring substrate10 (see FIG. 4A). The thickness of the insulating resin layer 14 on thesurface of each electrode pad 12 is 15 μm.

Next, on the insulating resin layer 14, an insulating resin layer 50 isformed, which differs from the insulating layer 14 in peeling-property(see FIG. 4A). The thickness of the insulating resin layer 50 is, e.g.,30 μm and may be within a range of 15 μm to 50 μm.

If a resin capable of being peeled by a certain solvent is used as theinsulating resin layer 50, a resin hard to peel with this solvent isused as the insulating resin layer 14. The reason for forming theinsulating resin layer 50 differing in peeling-property from theinsulating resin layer 14 is that the insulating resin layer 50 is madeto selectively be peeled in a post process.

If, e.g., a solder resist is used as the material of the insulatingresin layer 14, e.g., an epoxy-based thermosetting resin can be used asthe material of the insulating resin layer 50. The insulating resinlayer 50 can be peeled by, e.g., an organic solvent. However, theinsulating resin layer 14 is difficult to be peeled by an organicsolvent.

Next, the opening 15 penetrating through the insulating resin layers 14and 50 and reaching the electrode pad 12 is formed by laser processing(see FIG. 4B). Subsequently, a desmear treatment for removing a smear(i.e., a resin residue) generated by laser processing is performed. Thedesmear treatment is to remove a smear (i.e., a resin residue) using,e.g., a permanganic acid solution.

A laser-beam is attenuated in a depth direction. Thus, the shape of theopening 15 formed by laser processing is a tapered-shape whose upperpart is opened wide, as illustrated in FIG. 4A. The laser processing isperformed using, e.g., a carbon dioxide laser.

The shape of the opening 15 widened upward is such that the diameter ofa bottom part of the opening 15 is 40 μm, that the diameter of an upperpart is 55 μm, and that the spread-angle is 10 degrees.

The shape of the opening 15 widened upward is a tapered-shape configuredsuch that the diameter of the bottom is within a range of 30 μm to 60μm, that the diameter of the top is within a range of 40 μm to 100 μm,and that the spread-angle is within a range of 5 degrees to 30 degrees.

Next, the electrically-conductive layer 16 is formed on the electrodepad 12 in each opening 15 (see FIG. 4C).

Incidentally, the electrically-conductive layers 16 are formedconcurrently when the electrically-conductive layers 34 are respectivelyformed on the electrode pads 30 on the surface of the wiring substrate10, which is connected to the motherboard. Therefore, theelectrically-conductive layers 16 are not formed if theelectrically-conductive layers 34 are respectively formed on theelectrode pads 30 on the surface of the wiring substrate 10, which isconnected to the motherboard, in a state in which the surface of thewiring substrate 10, on which the semiconductor chip is mounted, ismasked. According to the present embodiment, the electrically-conductivelayers 34 are respectively formed on the electrode pads 30 on thesurface of the wiring substrate 10, which is connected to themotherboard, in a state in which the surface of the wiring substrate 10,on which the semiconductor chip is mounted, is not masked. Consequently,the electrically-conductive layers 16 are formed on the electrode pads12, respectively.

The electrically-conductive layers 16 are Ni/Pd/Au plating layers ineach of which Ni-layer, Pd-layer, and Au-layer are sequentially stackedby the electroless plating from the bottom side, as viewed in FIGS. 4Ato 4C. The electrically-conductive layers 34 concurrently formed areNi/Pd/Au plating layers in each of which Ni-layer, Pd-layer, andAu-layer are sequentially stacked by the electroless plating from thetop side, as viewed in FIG. 1.

The thickness of Ni-layer is, e.g., 5 μm and may be within a range of0.05 μm to 10 μm. The thickness of Pd-layer is, e.g., 0.1 μm and may bewithin a range of 0.02 μm to 0.2 μm. The thickness of Au-layer is, e.g.,0.1 μm and may be within a range of 0.01 μm to 0.5 μm.

Next, the seed layer 18 is formed on the entire surface of eachelectrically-conductive layer 16 (see FIG. 5A). The seed layer 18 isformed by, e.g., electroless plating on the top surface of theinsulating resin layer 50, the inner side surface of the opening 15 ofthe insulating resin layer 50, the inner side surface of the opening 15of the insulating resin layer 14, and the top surface of theelectrically-conductive layer 16.

The seed layer 18 is made of, e.g., copper, copper alloy, or the like.The thickness of the seed layer 18 is 0.5 μm and may be within a rangeof 0.2 μm to 2 μm.

Next, the entire surface of the seed layer 18 is coated with a dry filmresist (DFR) 52. Then, patterning is performed on the dry film resist 52to cover with exposure and development the top surface of the seed layer18 on the insulating resin layer 50 and to form an opening 53 from whicha region including the opening 15 on the electrode pad 12 is exposed(see FIG. 5B). The dimensions of the openings 53 formed on the dry filmresist 52 are set to be larger than the dimensions of the openings 15formed on the insulating resin layers 14 and 50.

Next, the metal layer 20 is formed on each region that is not coveredwith the dry film resist 52 (see FIG. 5C). The metal layer 20 is formedon the seed layer 18 by, e.g., electrolytic plating that uses the seedlayer 18 for electric-power feeding. The metal layer 20 is made of ametal whose melting point is higher than the melting point of the solderof the solder member 22. The thickness of the metal layer 20 is, e.g., 2μm and may be within a range of 0.5 μm to 5 μm.

The metal layer 20 is shaped to have the bottom portion 20 a and thecylindrical portion 20 b formed integrally with the bottom portion 20 asuch that the cylindrical portion 20 b is opened wide at an upper partthereof.

Next, the solder member 22 is formed on each metal layer 20 (see FIG.6A). The solder member 22 is formed on the bottom portion 20 a and inthe cylindrical portion 20 b of each metal layer 20 by filling solder onthe metal layer 20 through the electrolytic plating that uses the seedlayer 18 for electric-power feeding. Thus, the plural bump structures 24are formed, which includes the metal layer 20 and the solder member 22filled in the metal layer 20.

Next, the dry film resist 52 covering the top surface of the seed layer18 on the insulating resin layer 50 is removed (see FIG. 6B).

Next, the seed layer 18 exposed on the insulating resin layer 50 isremoved by flash etching (see FIG. 6C).

The entire chip-mounting-surface is polished and planarized by chemicalmechanical polishing (CMP) (see FIG. 7A). The insulating resin layer 50,the metal layer 20 and the solder member 22 are polished until the metallayer 20 and the solder member 22 are not left on the insulating resinlayer 50. Thus, the entire chip-mounting-surface is planarized.

Alternatively, when the entire surface is polished and planarized bychemical mechanical polishing (CMP), the seed layer 18 on the insulatingresin layer 50 may be removed, without etching removal of the seed layer18 by flash etching.

Next, the exposed insulating resin layer 50 is removed by a solvent (seeFIG. 7B). The insulating resin layer 50 is selectively peeled using,e.g., an organic solvent. The insulating resin layer 14 is not peeled byan organic solvent. Thus, the insulating resin layer 14 is left.

Next, solder reflowing is performed, so that the top-part of the soldermember 22 is rounded due to surface tension (see FIG. 7C). If Sn is usedas the material of the solder member 22, the solder reflowing isperformed by heating the solder member 22 to 250° C. The solder member22 is molten by the solder reflowing. However, the metal layer 20 is notmolten. Thus, only the top-part of the solder member 22 is rounded. Thefundamental bump structure is not changed. Incidentally, the solderreflowing may be omitted.

Incidentally, in steps respectively illustrated in FIGS. 5B and 5C, themetal layer 20 may be formed on the entire surface of the seed layer 18without using the dry film resist 52. In such a case, when the entiresurface of the seed layer 18 is planarized by chemical mechanicalpolishing (CMP), without removing the seed layer 18 by flash etching(see FIG. 6C), the metal layer 20 and the seed layer 18 on theinsulating resin layer 50 are removed by polishing.

Second Embodiment

A bump structure according to a second embodiment is described belowwith reference to FIGS. 8 to 13.

Wiring Substrate

A wiring substrate having a bump structure according to the secondembodiment is described with reference to FIG. 8. FIG. 8 is across-sectional diagram illustrating a wiring substrate having a bumpstructure according to the present embodiment. Each component which isthe same as that of the wiring substrate having the bump structureaccording to the first embodiment is designated with the same referencenumeral that designates the same component of the wiring substrateaccording to the first embodiment. Thus the description of such acomponent is omitted or simplified.

The bump structure according to the second embodiment is featured inthat the electrically-conductive layer 16 in the bump structureaccording to the first embodiment is not provided in the bump structureaccording to the second embodiment.

The internal structure of a wiring substrate 10 according to the presentembodiment is indicated by dashed lines in FIG. 8. The detaileddescription of the internal structure of the wiring substrate 10 isomitted.

In FIG. 8, the top surface of the wiring substrate 10 is achip-mounting-surface on which a semiconductor chip (not shown) ismounted. The bottom surface of the wiring substrate 10 is amotherboard-connection-surface connected to a motherboard (not shown).

Plural electrode pads 12 are formed on a chip-mounting-surface of thewiring substrate 10 at a small pitch compatible with the pitch of pluralelectrode posts (not shown) of a semiconductor chip (not shown) to bemounted.

On the chip-mounting-surface of the wiring substrate 10, an insulatingresin layer 14 is formed so as to cover the entire electrode pads 12.

An opening 15 tapered to be opened wide at an upper part thereof isformed on each electrode pad 12 in the insulating resin layer 14.

Each metal layer 20 is formed via a seed layer 18 on the side wall ofthe tapered-shape opening 15 of the insulating resin layer 14. Each ofthe seed layer 18 and the metal layer 20 is protruded upwardly from theinsulating resin layer 14. The metal layer 20 includes the bottomportion 20 a and the cylindrical portion 20 b that is formed integrallywith the bottom portion 20 a and opened wide at an upper part thereof.The solder member 22 is formed by filling the inside of the cylindricalportion 20 b of the metal layer 20 with solder. The metal layer 20 isformed using a metal whose melting point is higher than the meltingpoint of the solder member 22.

On the motherboard-connection-surface of the wiring substrate 10, whichis connected to the motherboard, plural electrode pads 30 are formed ata pitch compatible with the pitch of plural electrodes (not shown) ofthe motherboard (not shown) on which the wiring substrate 10 is mounted.

The opening 33 is formed on each electrode pad 30 in the insulatinglayer 32. The electrically-conductive layer 34 is formed on eachelectrode pad 30.

For example, in FIG. 8, the electrically-conductive layer 34 is aNi/Pd/Au plating layer in which Ni-layer, Pd-layer, and Au-layer arestacked sequentially from the top side.

The solder member 36 is formed on each electrically-conductive layer 34.

Semiconductor Apparatus

A semiconductor apparatus configured by mounting a semiconductor chip ona wiring substrate having a bump structure according to the presentembodiment is described below with reference to FIG. 9. FIG. 9 is across-sectional diagram illustrating a semiconductor apparatus that asemiconductor chip is mounted on a wiring substrate having a bumpstructure according to the present embodiment. Each component which isthe same as that according to the semiconductor apparatus that thesemiconductor chip is mounted on the wiring substrate having a bumpstructure according to the first embodiment is designated with the samereference numeral that designates the same component. Thus, thedescription of such a component is omitted or simplified.

As illustrated in FIG. 9, the plural electrode posts 42 are formed at asmall pitch on the semiconductor chip 40 to be mounted. The electrodepost 42 is, e.g., a columnar electrode post formed by copper-plating orthe like. The plural electrode pads 12 on the chip-mounting-surface ofthe wiring substrate 10 are formed at a pitch such that this pitch iscompatible with the pitch of the plural electrode posts 42 of thesemiconductor chip. The plural bump structures 24 each including themetal layer 20 and the solder member 22 are respectively formed on theplural electrode pads 12.

The plural electrode posts 42 on the semiconductor chip 40 arerespectively joined to the plural bump structures 24 on the wiringsubstrate 10.

Thus, a semiconductor apparatus is formed by mounting the semiconductorchip 40 on the wiring substrate 10.

As described above, according to the present embodiment, advantagessimilar to those of the first embodiment are obtained. For example, eachsolder member 22 is covered around with the metal layer 20 whose meltingpoint is higher than the melting point of solder. Thus, when theelectrode posts 42 on the semiconductor chip 40 are respectivelyconnected to the solder members 22, the molten solder member 22 can beprevented from being crushed and being laterally spread. In addition,because the solder member 22 is covered around with the metal layer 20,the growth of whisker due to the recrystallization of solder can besuppressed. Accordingly, the adjacent solder members 22 can be preventedelectrically connected and short-circuited by the crushed solder member22 or the whisker growing from the solder member 22.

According to the present embodiment, the electrically-conductive layers16 in the bump structures according to the first embodiment are notprovided. Thus, the electrical resistance between the bump structure 24and the electrode pad 12 can be reduced. Consequently, the electricalcharacteristics of the semiconductor apparatus can be improved.

In addition, because the electrically-conductive layer 16 in the bumpstructure according to the first embodiment is not provided, thecylindrical portion 20 b of the metal layer 20 can be formed more deeplyby an amount corresponding to the non-existent electrically-conductivelayer 16. Thus, if the distance of the semiconductor chip 40 to thewiring substrate 10 is too short, the electrode post 42 on thesemiconductor chip 40 can be more prevented, for the deeply formedcylindrical portion 20 b, from contacting with the bottom portion 20 aof the metal layer 20 so as to damage the electrode post 42 and themetal layer 20.

In addition, because the electrically-conductive layer 16 in the bumpstructure according to the first embodiment is not provided, theconsistent-contact between the seed layer 18 and the electrode pad 12can be enhanced.

Bump Structure Manufacturing Method

A manufacturing method for a bump structure according to the presentembodiment is described below with reference to FIGS. 10 to 13C. FIGS.10 to 13C are process cross-sectional diagrams illustrating a method ofmanufacturing a bump structure according to the present embodiment. Eachcomponent which is the same as that according to the method ofmanufacturing the bump structure according to the first embodiment isdesignated with the same reference numeral that designates the samecomponent of the wiring substrate according to the first embodiment.Thus the description of such a component is omitted or simplified.

First, the insulating resin layer 14 is formed to cover the entireelectrode pads 12 serving as an outermost layer of the wiring substrate10 (see FIG. 10A).

Next, on the insulating resin layer 14, an insulating resin layer 50 isformed, which differs from the insulating layer 14 in thepeeling-property (see FIG. 10A).

Materials similar to the materials used in the method of manufacturingthe bump structure according to the first embodiment can be used asthose of the insulating resin layers 14 and 50.

Next, the opening 15 penetrating through the insulating resin layers 14and 50 and reaching the electrode pad 12 is formed by laser processing(see FIG. 10B). Subsequently, a desmear treatment for removing a smear(i.e., a resin residue) generated by laser processing is performed. Thedesmear treatment is to remove a smear (i.e., a resin residue) using,e.g., a permanganic acid solution.

A laser-beam is attenuated in a depth direction. Thus, the shape of theopening 15 formed by laser processing is a shape tapered to be widenedupward, as illustrated in FIG. 10B.

Then, according to the present embodiment, an electrically-conductivelayer is not formed on each electrode pad 12 in the opening 15, whilethe electrically-conductive layer 34 is formed on each electrode pad 30on the motherboard-connection-surface of the wiring substrate 10.According to the present embodiment, when the electrically-conductivelayer 34 is formed on each electrode pad 30 on themotherboard-connection-surface of the wiring substrate 10, thechip-mounting-surface of the wiring substrate 10 is masked. Thus, anelectrically-conductive layer is prevented from being formed on thechip-mounting-surface.

Next, the seed layer 18 is formed on the entire surface of eachelectrically-conductive layer 16 (see FIG. 11A).

Next, the entire surface of the seed layer 18 is coated with the dryfilm resist (DFR) 52. Then, patterning is performed on the dry filmresist 52 to cover with exposure and development the top surface of theseed layer 18 on the insulating resin layer 50 and to form an opening 53from which a region including the opening 15 on the electrode pad 12 isexposed (see FIG. HB). The dimensions of the openings 53 formed on thedry film resist 52 are set to be larger than the dimensions of theopenings 15 formed on the insulating resin layers 14 and 50.

Next, the metal layer 20 is formed on an area which is not covered bythe dry film resist 52 (FIG. 11C). The metal layer 20 is made of a metalwhose melting point is higher than the melting point of the solder ofthe solder member 22.

The metal layer 20 is shaped to have the bottom portion 20 a and thecylindrical portion 20 b formed integrally with the bottom portion 20 asuch that an upper part of the cylindrical portion 20 b is opened wide.

Next, the solder member 22 is formed on each metal layer 20 (see FIG.12A).

Next, the dry film resist 52 covering the top surface of the seed layer18 on the insulating resin layer 50 is removed (see FIG. 12B).

Next, the seed layer 18 exposed on the insulating resin layer 50 isremoved by flash etching (see FIG. 12C).

The entire chip-mounting-surface is polished and planarized by chemicalmechanical polishing (CMP) (see FIG. 13A).

The seed layer 18 on each insulating resin layer 50 may be removed whenthe entire chip-mounting-surface is polished and planarized by chemicalmechanical polishing (CMP), without removing the seed layer 18 by flashetching, after the dry film resist 52 is removed.

Next, the exposed insulating resin layer 50 is removed by a solvent (seeFIG. 13B). The insulating resin layer 50 is selectively peeled using,e.g., an organic solvent. The insulating resin layer 14 is not peeledoff by an organic solvent. Thus, the insulating resin layer 14 is left.

Next, solder reflowing is performed, so that the top-part of the soldermember 22 is rounded due to surface tension (see FIG. 13C).Incidentally, the solder reflowing may be omitted.

Third Embodiment

A bump structure according to a third embodiment is described below withreference to FIGS. 14 to 15C.

Wiring Substrate

A wiring substrate having a bump structure according to the thirdembodiment is described with reference to FIG. 14. Each component whichis the same as that of the wiring substrate having the bump structureaccording to the first embodiment is designated with the same referencenumeral that designates the same component of the wiring substrateaccording to the first embodiment. Thus the description of such acomponent is omitted or simplified.

The bump structure according to the present embodiment is featured inthat the bump structure according to the third embodiment differs inshape from the bump structure according to the first embodiment.

The internal structure of the wiring substrate 10 according to thepresent embodiment is indicated by dashed lines in FIG. 14. The detaileddescription of the internal structure of the wiring substrate 10 isomitted.

In FIG. 14, the top surface of the wiring substrate 10 is achip-mounting-surface on which a semiconductor chip (not shown) ismounted. The bottom surface of the wiring substrate 10 is amotherboard-connection-surface connected to a motherboard (not shown).

Plural electrode pads 12 are formed on the chip-mounting-surface of thewiring substrate 10 at a small pitch compatible with the pitch of pluralelectrode posts (not shown) of a semiconductor chip (not shown) to bemounted.

On the chip-mounting-surface of the wiring substrate 10, the insulatingresin layer 14 is formed.

The opening 15 tapered such that an upper part is opened wide is formedon each electrode pad 12 in the insulating resin layer 14.

Each metal layer 20 is formed via the seed layer 18 on the side wall ofthe tapered-shape opening 15 of the insulating resin layer 14. Each ofthe seed layer 18 and the metal layer 20 is protruded upwardly from theinsulating resin layer 14. The metal layer 20 includes the bottomportion 20 a and the cylindrical portion 20 b that is formed integrallywith the bottom portion 20 a and opened wide at an upper part. Accordingto the present embodiment, the top-part of the cylindrical portion 20 bis extended in a direction perpendicular to the central axis of thecylindrical portion 20 b.

The solder member 22 is formed by filling the inside of the cylindricalportion 20 b of the metal layer 20 with solder. The metal layer 20 isformed using a metal whose melting point is higher than the meltingpoint of the solder member 22.

On the motherboard-connection-surface of the wiring substrate 10, pluralelectrode pads 30 are formed at a pitch compatible with the pitch ofplural electrodes (not shown) of a motherboard (not shown) on which thewiring substrate 10 is mounted.

The pitch of the plural electrode pads 30 is compatible with the pitchof plural electrodes (not shown) on the motherboard (not shown).

The insulating layer 32 is formed on the motherboard-connection-surfaceof the wiring substrate 10 to cover the electrode pads 30.

The opening 33 is formed on each electrode pad 30 in the insulatinglayer 32. The electrically-conductive layer 34 is formed on eachelectrode pad 30.

The solder member 36 is formed on each electrically-conductive layer 34.

As described above, according to the present embodiment, advantagessimilar to those of the first embodiment are obtained. For example, eachsolder member 22 is covered around with the metal layer 20 whose meltingpoint is higher than the melting point of solder. Thus, when theelectrode posts 42 on the semiconductor chip 40 are respectivelyconnected to the solder members 22, the molten solder member 22 can beprevented from being crushed and being laterally spread. In addition,because the solder member 22 is covered around with the metal layer 20,the growth of whisker due to the recrystallization of solder can besuppressed. Accordingly, the adjacent solder members 22 can be preventedelectrically connected and short-circuited by the crushed solder member22 or the whisker growing from the solder member 22.

In addition, according to the present embodiment, the top-part of thecylindrical portion 20 b of the metal layer 20 is extended in adirection perpendicular to the central axis of the cylindrical portion20 b. Thus, as compared with the bump structures according to the firstembodiment and the second embodiment, the substantial joint portion ofthe bump structure is more enlarged. Even if a deviation of theformation-position, at which each bump structure is formed, from thecorresponding electrode post 42 on the semiconductor chip 40 occurs,each bump structure 24 can favorably be connected to the correspondingelectrode 42.

Bump Structure Manufacturing Method

A manufacturing method for a bump structure according to the presentembodiment is described below with reference to FIG. 15. FIG. 15 is aprocess cross-sectional diagram illustrating a method of manufacturing abump structure according to the present embodiment. Each component whichis the same as that according to the method of manufacturing the bumpstructure according to the first embodiment is designated with the samereference numeral that designates the same component of the wiringsubstrate according to the first embodiment. Thus the description ofsuch a component is omitted or simplified.

The steps illustrated in FIGS. 4A to 6C of the method of manufacturingthe bump structure according to the third embodiment are similar to thecorresponding steps of the method of manufacturing the bump structureaccording to the first embodiment.

The seed layers 18 exposed on the insulating resin layer 50 are removedby flash etching (see FIG. 15A), similarly to a case illustrated in FIG.6C. Then, the exposed insulating resin layer 50 is removed by a solvent(see FIG. 15B). Consequently, the seed layers 18 and the metal layers 20are protruded upwardly from the insulating resin layer 14. Each metallayer 20 includes the bottom portion 20 a, and the cylindrical portion20 b that is formed integrally with the bottom portion 20 a and openedwide at an upper part. According to the third embodiment, the top-partof the cylindrical portion 20 b is extended in a direction perpendicularto the central axis of the cylindrical portion 20 b.

Next, solder reflowing is performed, so that the top-part of the soldermember 22 is rounded due to surface tension (see FIG. 15C).Incidentally, the solder reflowing may be omitted.

Modified Embodiments

The above embodiments are examples. Various modifications of the aboveembodiments can be made, if necessary.

For example, according to the above embodiments, the bump structures areformed on the electrode pads on the wiring substrate. However, the bumpstructure may be formed on the pad of the semiconductor chip.

In addition, any types of interconnection substrates, such as asingle-sided board configured so that a pattern is provided on only asingle side, a double-sided board configured so that patterns arerespectively provided on both sides, a multi-layer wiring substrateconfigured by stacking insulating-layers and wiring-layers, aninterposer relaying between the semiconductor chip and a circuit board,can be used as the wiring substrate.

The wiring substrate is not limited to a buildup substrate using aninsulating layer made of resin, and a core substrate. Various types ofwiring substrates, such as a coreless substrate, may be used.

According to the above embodiments, the wiring substrate is connected tothe motherboard via the solder member (solder bump). However, othermethods, such as a pin contact method and a wire bonding method, may beused.

Various aspects of the subject matter described herein are set outnon-exhaustively in the following numbered clauses:

1. A method of manufacturing a bump structure provided on an electrodepad, comprising:

forming a first resin layer on the electrode pad;

forming, on the first resin layer, a second resin layer differing inpeeling-property from the first resin layer;

forming, in each of the first resin layer and the second resin layer, afirst opening whose upper part is opened wide;

forming, on an inner wall of the first opening, a metal layer made of ametal which is higher in melting-point than a solder member;

filling the solder member in the metal layer; and removing the secondresin layer.

2. The method of manufacturing a bump structure according to claim 1,further comprising:

planarizing an entire surface after filling the solder member and beforeremoving the second resin layer.

3. The method of manufacturing a bump structure according to claim 1,further comprising:

forming a resist layer in which a second opening including the firstopening is formed on the second resin layer, after forming the firstopening and before forming the metal layer;

forming the metal layer using the resist layer as a mask in the formingof the metal layer;

filling the solder member using the resist layer as a mask in thefilling of the solder member; and

peeling the resist layer after filling the solder member and beforeremoving the second resin layer.

The preferred embodiments of the invention have been described above indetail. However, the invention is not limited to the embodimentsdescribed above. Various modifications and alteration to the embodimentsdescribed above can be made within the scope of gist described inclaims.

What is claimed is:
 1. A bump structure provided on an electrode pad,comprising: a solder member; and a metal layer having a cylindricalportion covering a side surface of the solder member, the metal layerbeing made of a metal which is higher in melting point than the soldermember, wherein an upper part of the cylindrical portion of the metallayer is opened wide.
 2. The bump structure according to claim 1,wherein the solder member is shaped like an inverted truncated-cone,whose upper part is wide.
 3. The bump structure according to claim 1,wherein: the metal layer further includes a bottom portion covering abottom surface of the solder member, and the bottom portion of the metallayer is electrically connected to the electrode pad; and abottom-side-part of the metal layer is embedded in an insulating resinlayer formed on the electrode pad, and a top-side-part of the metallayer is protruded from the insulating resin layer.
 4. The bumpstructure according to claim 1, wherein: a top-part of the cylindricalportion of the metal layer is extended in a direction perpendicular to acentral axis of the cylindrical portion.
 5. The bump structure accordingto claim 1, wherein: the solder member is made of Sn, Sn—Zn alloy, Sn—Cualloy, Sn—In alloy, or Sn—Ag alloy; and the metal layer is made of Ni orCo.
 6. A wiring substrate comprising: an electrode pad; and a bumpstructure provided on the electrode pad, the bump structure including asolder member, and a metal layer which has a cylindrical portioncovering a side surface of the solder member and is made of a metalhigher in melting point than the solder member, wherein an upper part ofthe cylindrical portion of the metal layer is opened wide.
 7. Asemiconductor apparatus comprising: a wiring substrate having anelectrode pad and a bump structure provided on the electrode pad, thebump structure including a solder member and a metal layer which has acylindrical portion covering a side surface of the solder member and ismade of a metal higher in melting point than the solder member, an upperpart of the cylindrical portion of the metal layer being opened wide;and a semiconductor chip mounted on the wiring substrate, and configuredto have an electrode that is connected to the bump structure.